Blow air cylinder for blow-molding hollow container

Abstract

A blow molding method by horizontal blow molding of piercing the wall of a parison having been extruded by an extruder with a blow nozzle is disclosed, which comprises moving forward the blow nozzle to pierce the parison, introducing blow air at least in the direction toward the bottom, i.e., opposite to the bottle neck and, after shaping of a hollow container by the blow air, forming an opening in the parison at a position in the vicinity of or above the blow nozzle-pierced portion to discharge the blow air having circulated inside the hollow container. In this blow mollding method, there is preferably used a blow air cylinder, which is constituted by (A) a blow nozzle having a mechanism for registering blowing inlets in at least part of a portion freely sliding forward and backward inside the body, having a tip portion with an outer diameter smaller than at about the center portion thereof and being of a shape of a closed injection needle, and having the blowing inlets located slightly at the back of the tip portion where the outer diameter is larger than that at the tip portion and smaller than that at the central portion and capable of introducing blow air in the direction toward the bottom, i.e., opposite to the bottle neck in an amount of 30% or more of the total blow air amount; and (B) a body provided outside and, at least partly, in contact with the blow nozzle.

What is claimed is: 
     
       1. A blow air cylinder comprising, in combination; a housing having a hollow interior and a guiding opening,   a blow nozzle having a generally tubular body which is slidably movable through said guiding opening of said housing forwardly and backwardly inside a molded body to be cooled, said molded body having one end intended to form a bottle neck and another end intended to form a bottom,   said tubular body of said blow nozzle having a tip portion including a solid sharp tip for penetrating a wall of said molded body,   a plurality of blowing inlets for emitting air therefrom being located at spaced locations about a circumference of said tubular body at a back side of said tip portion in a region of said tubular body having an outer diameter which is larger than that at said tip portion,   said plurality of blowing inlets being sized to supply a larger amount of blow air, in an amount of at least 30% of the total blow air amount, away from said neck end and toward said bottom of said molded body,   and means on said tubular body of said blow nozzle cooperating with said guiding opening of said housing for positioning said blow inlets with the inside of said molded body.   
     
     
       2. The blow air cylinder as described in claim 1, further comprising a discharge outlet for discharging blow air in the wall of the housing in the vicinity of the tip of the body. 
     
     
       3. The blow air cylinder as described in claim 1, further comprising an air-feeding inlet in the housing for permitting air to be introduced when the blow nozzle moves forward and for introducing blow air into the mold, and another air-feeding inlet in the housing for receiving air from the blow nozzle when it moves backward. 
     
     
       4. The blow air cylinder as described in claim 1, wherein said positioning mechanism comprises at least part of the tubular body of the blow nozzle  in! having an elliptical form in cross section, with a horizontal axis of the elliptical form being the major axis. 
     
     
       5. The blow air cylinder as described in claim 1, wherein the amount of blow air introduced in the direction toward the bottom of said molded body which is opposite to the bottle neck, is greater than that introduced in other directions.